STRUCTTJBE OF THE SPLEEN. 187 



LESSON XXXIV. 



STRUCTURE OF THE SPLEEN, SUPRARENAL CAPSULE, AND 

 THYROID BODY. 



] . SUCTIONS of the spleen stained with lueinatoxylin. Notice the trabeculie 

 extending into the substance of the organ from the capsule. Notice also that 

 the glandular substance is of two kinds, (1) lymphoid tissue accumulated 

 round the small arteries and here and there massed to form lymphoid nodules 

 the Malpighian corpuscles of the spleen and (2) a tissue consisting of a 

 reticulum of branched and flattened cells containing blood in its interstices 

 and pervaded by capillaries and venous radicles. 



Sketch part of a section under a low power and a small portion of the 

 reticulum under a high power. 



2. Sections across a suprarenal capsule. Examine first with a low power, 

 noticing the general arrangement and extent of the cortical and medullary 

 parts of the organ, making a general sketch which shall include both. After- 

 wards sketch carefully under the high power a group of cells from each part 

 of the organ. 



3. Sections of the thyroid body stained with hsematoxylin. Notice the 

 vesicles lined with cubical epithelium and filled with a " colloid " substance 

 which becomes stained by the haematoxylin. Sketch one or two vesicles. 

 Measure several vesicles. 



THE SPLEEN. 



The spleen is the largest of the so-called ductless glands. It appears 

 to be functionally connected in some way with the blood, white blood- 

 corpuscles being certainly formed and coloured blood-corpuscles being 

 probably submitted to destruction within it. 



Like the lymphatic glands, the spleen is invested with a fibrous and 

 muscular capxule (fig. 220, A), and this again has a covering derived 

 from the serous membrane. The capsule sends fibrous bands or tra- 

 beculse (b) into the organ, and these join with a network of similar 

 trabeculse which pass into the gland at the hilurn along with the blood- 

 vessels. In the interstices of the fibrous framework thus constituted 

 lies a soft pulpy substance containing a large amount of blood, and 

 therefore of a deep red colour, dotted within which are here and there 

 to be seen small whitish specks, the Malpighian cwpuscles of the spleen 

 (<; r). These are composed of lymphoid tissue which is gathered up 



